The rules state that you can only have 3 total between scored and in scored objectives. Does that mean that once you have 3 scored secret objectives you are no longer eligible to draw a new one? If you can, do you have to give up the previously scored points to draw a new one?
You can only discard unscored secret objectives. So if you find yourself with 3 scored objectives and draw a 4th, you must discard it.
I seem to remember hearing of people using the strategy of focusing heavily on secret objectives to win the game, but how can that be if 3 is the limit?
You only need 10 points to win, so secret objectives can account for almost 1/3rd of your total victory. You can choose to ignore them and work on the public objectives and Mecatol Rex, or you can score your secrets for a quicker victory.